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Mary Cheng

Doing postgraduate work in the molecular origins of pain would be enough to keep most students busy, but when Mary Cheng was working on her PhD in the Department of Medical Biophysics at the University of Toronto in the late ‘90s, she often got caught up in reading outside of her field. It was while doing this extracurricular perusing that she made a pivotal discovery: she had a keen interest in the circadian clock.

“Some of the most interesting papers that I read were about the molecular mechanisms underlying biological timekeeping,” says Cheng, currently an Assistant Professor in the Department of Biology at U of T Mississauga studying the internal biological clock’s impact on health issues.

“Unlike other research areas that I’ve been involved in, the study of circadian rhythms struck me as being cool yet quirky– even otherworldly – until other scientists started discovering many of the clock genes in the late 1990s to early 2000s. After that I was hooked,” says Cheng, who held a Canada Research Chair in the Genetics of Biological Timing at the University of Ottawa prior to coming to UTM.

These days she is most interested in identifying genes that regulate the photic entrainment process. “Entrainment is without a doubt the most important and fundamental function of our circadian clock because our body’s clock must be able to predict “real” time, as in the outside-world time, so that we can organize our behaviour and physiology optimally according to a world of limited resources,” explains Cheng. Photic entrainment allows us to daily reset our internal clock so it synchronizes with the geophysical, external clock, and it also kicks in when travelling and adjusting to new time zones. Even in these darker days of winter, our clocks adjust to the variations on daylength.

Cheng’s work involves studying the behaviour of mice and measuring the circadian rhythms of their locomotor activity, and also identifying how certain genes affect the circadian clock function in mice.

Though her research focus may have changed slightly since she started her academic career, Cheng knew from an early age that research was what she wanted to do. Initially in high school she had intentions of becoming a medical doctor, but after completing a year at university, she was swayed towards her current path. “When I was 19 and after having completed the first year of my BSc in biochemistry, I volunteered for a summer in a research lab at the University of Calgary,” recalls Cheng. “After a week of working in the lab, I was absolutely in love with research. I knew that I had found my calling. I haven’t looked back since.”